Aircraft, such as commercial airliners, typically include control surfaces or devices mounted on the wings to improve the aerodynamic performance of the aircraft. Such control surfaces typically include wing leading edge devices and wing trailing edge devices which may be extended and/or deflected during different phases of flight to alter the lift and/or drag characteristics of the wings. For example, commercial airliners typically include trailing edge flaps which may be extended during takeoff, approach, landing, and other flight phases to increase the area and camber of the wings to increase the wing lift characteristics.
Aircraft regulatory bodies such as the Federal Aviation Administration require that aircraft meet minimum performance standards for different phases of flight. For example, Federal Aviation Regulation (FAR) 25.121 specifies a minimum climb gradient capability for an aircraft during a critical engine inoperative situation. For a twin-engine aircraft, FAR 25.121(d) specifies a minimum approach-climb gradient capability of 2.1% with one engine inoperative, the landing gear retracted, the aircraft in an approach flaps configuration, and the remaining engine at a go-around thrust setting. In addition, FAR 25.121(d) specifies that the stall speed in the approach configuration must not exceed 110 percent of the stall speed (“the 110% speed rule”) for the related all-engines-operating landing configuration.
FAR 25.119 specifies a minimum landing-climb gradient capability of 3.2% with all engines operating, the aircraft in a landing flaps configuration, and the engines generating as much thrust as is possible eight seconds after advancing the throttles to the go-around thrust setting. FAR 25.1001(a) requires that a fuel jettisoning system must be installed unless it is shown that the airplane meets the climb requirements of FAR 25.119 and 25.121(d) at maximum takeoff weight, less the actual or computed weight of fuel necessary for a 15-minute flight comprising a takeoff, go-around, and landing at the airport of departure. FAR 25.1001(b) requires that if a fuel jettisoning system is required, it must be capable of jettisoning enough fuel within 15 minutes, starting with the weight given in FAR 25.1001(a), to enable the airplane to meet the climb requirements of FAR 25.119 and 25.121(d). The aircraft must be capable of meeting the more restrictive of the approach-climb requirement and the landing-climb requirement.
Conventional aircraft typically allow for extending the flaps to a limited number of flap settings. For example, certain aircraft may have flap detent settings of Flaps 1, Flaps 5, Flaps 15, Flaps 20, Flaps 25, or Flaps 30. During final approach to an airport, Flaps 25 or 30 may be selected for landing the aircraft. The flap setting will be reduced to Flaps 20 if the landing is aborted and a go-around operation is initiated. However, if the aircraft takes off with the maximum takeoff weight, the aircraft may not be able to meet the approach-climb and landing-climb requirements at the departure airport using Flaps 20 as the go-around flap setting. To compensate, the aircraft may be required to take off with a reduced gross weight by reducing the payload of the aircraft. In this regard, conventional flap control systems and/or aircraft with such conventional flap control systems may be limited in their performance and/or operational capability.